The coatomer is a protein complex[1] that coats membrane-bound transport vesicles. Two types of coatomers are known:
- COPI (retrograde transport from trans-Golgi network to cis-Golgi network and endoplasmic reticulum)
- COPII (anterograde transport from ER to the cis-Golgi)
Coatomers are functionally analogous and evolutionarily homologous to clathrin adaptor proteins, also known as adaptins,[2] which regulate endocytosis from the plasma membrane and transport from the trans-Golgi network to lysosomes.
https://en.wikipedia.org/wiki/Coatomer
Archain is a protein located on chromosome 11. Also known as ARCN1, it plays a role in eukaryotic cell biology.
It is part of the COPI coatomer complex.[1]
https://en.wikipedia.org/wiki/Archain
ADP ribosylation factors (ARFs) are members of the ARF family of GTP-binding proteins of the Ras superfamily. ARF family proteins are ubiquitous in eukaryotic cells, and six highly conserved members of the family have been identified in mammalian cells. Although ARFs are soluble, they generally associate with membranes because of N-terminus myristoylation. They function as regulators of vesicular traffic and actinremodelling.
The small ADP ribosylation factor (Arf) GTP-binding proteins are major regulators of vesicle biogenesis in intracellular traffic.[1] They are the founding members of a growing family that includes Arl (Arf-like), Arp (Arf-related proteins) and the remotely related Sar (Secretion-associated and Ras-related) proteins. Arf proteins cycle between inactive GDP-bound and active GTP-bound forms that bind selectively to effectors. The classical structural GDP/GTP switch is characterised by conformational changes at the so-called switch 1 and switch 2 regions, which bind tightly to the gamma-phosphate of GTP but poorly or not at all to the GDP nucleotide. Structural studies of Arf1 and Arf6 have revealed that although these proteins feature the switch 1 and 2 conformational changes, they depart from other small GTP-binding proteins in that they use an additional, unique switch to propagate structural information from one side of the protein to the other.
The GDP/GTP structural cycles of human Arf1 and Arf6 feature a unique conformational change that affects the beta2beta3 strands connecting switch 1 and switch 2 (interswitch) and also the amphipathic helical N-terminus. In GDP-bound Arf1 and Arf6, the interswitch is retracted and forms a pocket to which the N-terminal helix binds, the latter serving as a molecular hasp to maintain the inactive conformation. In the GTP-bound form of these proteins, the interswitch undergoes a two-residue register shift that pulls switch 1 and switch 2 up, restoring an active conformation that can bind GTP. In this conformation, the interswitch projects out of the protein and extrudes the N-terminal hasp by occluding its binding pocket.
https://en.wikipedia.org/wiki/ADP_ribosylation_factor
p14ARF (also called ARF tumor suppressor, ARF, p14ARF) is an alternate reading frame protein product of the CDKN2A locus (i.e. INK4a/ARF locus).[1] p14ARF is induced in response to elevated mitogenic stimulation, such as aberrant growth signaling from MYC and Ras (protein).[2] It accumulates mainly in the nucleolus where it forms stable complexes with NPM or Mdm2. These interactions allow p14ARF to act as a tumor suppressor by inhibiting ribosome biogenesis or initiating p53-dependent cell cycle arrest and apoptosis, respectively.[3] p14ARF is an atypical protein, in terms of its transcription, its amino acid composition, and its degradation: it is transcribed in an alternate reading frame of a different protein, it is highly basic,[1] and it is polyubiquinated at the N-terminus.[4]
Both p16INK4a and p14ARF are involved in cell cycle regulation. p14ARF inhibits mdm2, thus promoting p53, which promotes p21 activation, which then binds and inactivates certain cyclin-CDK complexes, which would otherwise promote transcription of genes that would carry the cell through the G1/S checkpoint of the cell cycle. Loss of p14ARF by a homozygous mutation in the CDKN2A (INK4A) gene will lead to elevated levels in mdm2 and, therefore, loss of p53 function and cell cycle control.
The equivalent in mice is p19ARF.
https://en.wikipedia.org/wiki/P14arf
Coatomer subunit alpha is a protein that in humans is encoded by the COPA gene.[5][6]
https://en.wikipedia.org/wiki/COPA_(gene)
Small GTPases (EC 3.6.5.2), also known as small G-proteins, are a family of hydrolase enzymes that can bind and hydrolyze guanosine triphosphate (GTP). They are a type of G-protein found in the cytosol that are homologous to the alpha subunit of heterotrimeric G-proteins, but unlike the alpha subunit of G proteins, a small GTPase can function independently as a hydrolase enzyme to bind to and hydrolyze a guanosine triphosphate (GTP) to form guanosine diphosphate (GDP). The best-known members are the Ras GTPases and hence they are sometimes called Ras subfamilyGTPases.
A typical G-protein is active when bound to GTP and inactive when bound to GDP (i.e. when the GTP is hydrolyzed to GDP). The GDP can be then replaced by free GTP. Therefore, a G-protein can be switched on and off. GTP hydrolysis is accelerated by GTPase activating proteins (GAPs), while GTP exchange is catalyzed by guanine nucleotide exchange factors (GEFs). Activation of a GEF typically activates its cognate G-protein, while activation of a GAP results in inactivation of the cognate G-protein.Guanosine nucleotide dissociation inhibitors (GDI) maintain small GTPases in the inactive state.
Small GTPases regulate a wide variety of processes in the cell, including growth, cellular differentiation, cell movement and lipidvesicle transport.
https://en.wikipedia.org/wiki/Small_GTPase
Sec23 homolog A (S. cerevisiae), also known as SEC23A, is a proteinwhich in humans is encoded by the SEC23A gene.[5]
https://en.wikipedia.org/wiki/SEC23A
| COPI | |
|---|---|
| COPII |
https://en.wikipedia.org/wiki/Munc-18
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